The present invention relates to antennas and more particularly to a technique for stowing an antenna in a reduced volume while automatically deploying the antenna to a desired length during activation of a wireless device.
Many contemporary communications and navigation products have been developed that rely on earth-orbiting satellites to provide necessary communications and navigation signals. Examples of such products include satellite navigation systems, satellite tracking and locator systems, and communications systems which rely on satellites to relay the communications signals from one station to another. Such satellites can form part of various types of known satellite constellations and operate at various orbital altitudes, such as Low Earth Orbit (LEO), Medium Earth Orbit (MEO), or in geosynchronous orbit.
Advances in electronics in the areas of packaging, power consumption, miniaturization, and production, have generally resulted in the availability of such products in a portable package at a price point that is attractive for many commercial and individual consumers. However, one area in which further development is needed is the antenna used to provide communications with satellites. Typically, antennas suitable for use in the appropriate frequency range are larger than would be desired for use with a portable device. Often times, the antennas are implemented using microstrip technology. However, in such antennas, the feed networks are often larger than would be desired or exhibit unwanted characteristics.
Additionally, in applications where transmit and receive communications occur at different frequencies, dual-band antennas are often available only in less than desirable configurations. For example, one way in which a dual band antenna can be made is to stack two single-band quadrifilar helix antennas end-to-end, so that they form a single, common axis cylinder. A disadvantage of this solution, however, is that such an antenna is longer than would otherwise be desired for portable, or hand-held applications.
Another technique for providing dual-band performance has been to utilize two single band antennas, one tuned for each frequency. However, for hand-held units, the two antennas would have to be located in close proximity to one another. Unfortunately, two single band antennas, placed in close proximity on a portable, or hand-held device, create a bulky and unaesthetic unit, which is also undesirable. At the same time, when using satellite repeaters for signal transfer, the communications signals are circularly polarized, or become so through interaction with the atmosphere, and an antenna having good circular polarization is desired.
It has been discovered that antenna structures can be mounted on base support structures that rotate or bases that fold or "flip" the antenna into a deployed position above the telephone. However, such structures still consume more space than is desired, due in part to the length of the antenna elements, and provide complicated mechanical structures across which electrical connections to the antenna elements must be completed.
What is needed therefore, is an antenna in a small enough package such that it is suitable for portable and/or hand-held applications. It is also desirable that the feed structure for the antenna be reduced to a single input connection for many applications.